




















whereas the correct value is 237. 

Aug. 31, 1871 | 
2 mirror galvanometer, and the deflections noted at intervals of 
one minute, as the ball gradually cooled. 
The method of reducing the observations is explained at length 
in the paper. The differences of the Napierian logarithms of 
the differences of temperature of the junctions, indicated by the 
deflections, divided by the intervals of time, give the rate of 
cooling, and this, multiplied by a factor depending on the capa- 
city for heat of the ball, and on the extent of its surface, gives 
the quantity of heat emitted in gramme water units, in the unit 
of time per square centimetre, per 1° difference of temperatures. 
_ Formulz are given which express the results of the experiments 
very closely, and a table calculated by them exhibits the rates of 
emission for every 5° of difference throughout the range. 
The first and second series have a range of from 5° to 25° 
only, which was too small to give decided results, but the third 
and fourth series, made with a polished copper surface and a 
blackened surface respectively, gave variations on the emissive 
power from ‘000178 at 5° diff. of temperature to ‘000226 at 60° 
diff. for the blackened surface, and exhibit throughout a nearly 
constant ratio of about “694. 
On Wet and Dry Bulb Formule, by Prof. Everett. He said, 
August, Apjohn, and Regnault have investigated formule for 
determining the dew point, by calculation, from the temperatures 
of the dry and wet bulb thermometers ; but Regnault’s experi- 
ments on the specific heat of air were not performed till a later 
date, and all their authors have adopted in their investigations 
the value obtained by Delaroche and Berard, which is °267, 
But when this correct value 
is introduced into Regnault’s formula, the discrepancies which 
creased, and amount, on an average, to about 25 per cent. of the 
difference between wet bulb temperatures and dew point. August 
and Apjohn erred in assuming that the air which gives heat to the 
wet bulb falls to the temperature of the wet bulb, and becomes 
saturated. These two false assumptions would jointly produce 
no error in the result, if the depressions of temperature in the 
different portions of air affected were exactly proportional to 
their increments of vapour-tension, and if some of the air were 
saturated at the temperature of the wet bulb. But it is probable 
that, when there is little or no wind, the mass of air which 
falls sensibly in temperature is larger than that which receives 
a sensible accession of vapour, and that, in high wind, the sup- 
position that some of the air has fallen to the temperature of the 
wet bulb, is more nearly fulfilled than the supposition that it 
has taken up enough vapour to saturate it. The effect of radia- 
tion, which is ignored in the formule, leads in the same direction 
as these two inequalities, and all three are roughly compensated 
by attributing to air a greater specific heat than it actually has. 
The discrepancies above referred to are thus explained. 
On a New Key for the Morse Printing Telegraph, by Prof. 
Zenger. 
On Clean and Uncelean Surfaces in Voltaic Action, by T. 
Bloxam. 
On the Corrosion of Copper Plates by Nitrate of Silver, by J. H. 
Gladstone, F.R.S., and A. Tribe, F.C.S. In some recent ex- 
periments in Chemical Dynamics the authors had occasion to 
study the action of nitrate of silver on copper plates in various 
positions. They observed that when the plate was vertical there 
was rather more corrosion at the bottom than at the top. This 
is easily accounted for by the upward current which flows along 
the surface of the deposited crystals, and which necessitates a 
movement of the nitrate of silver solution towards the copper 
plate, especially impinging on the lower part. It was also found 
that when the copper plate was varnished on one side, it pro- 
duced rather more than half the previous decomposition, and was 
more corroded at the edges of the varnish, By making patterns 
with the varnish this edge action became very evident. This 
was explained by the fact that the long crystals of silver growing 
out from the copper at the border can spread their branches into 
the open space at the side, and so draw their supply froma larger 
mass of solution than the crystals in the middle can do; and in- 
creased crystallisation of silver means increased solution of copper. 
This was proved by making the varnish a perpendicular wall 
instead of a thin layer, when the greater corrosion was not ob- 
tained. In a plate completely surrounded with liquid the greatest 
growthof crystals is also evidently from the angles, It was likewise 
obseryed that if a vertical plate be immersed, the lower part in 
nitrate of copper, and the upper part in nitrate of silver, there is 
greater corrosion about the point of junction. This was attribut- 
able to the greater conduction of the stronger liquid. 
he found to exist between calculation and observation are in- | 
NATURE 

353 
The Influence of the Moon on Rainfall, by W. Pengelly, F.R.S. 
On Units of Force and Energy, by Prof. Everett, D.C.L. 
All authorities are agreed that the units of length, time, mass, 
and force ought to be so settled as to satisfy the condition that 
unit force acting for unit time on unit mass generates unit velocity. 
Now, of the four elements, length, time, mass, and force, the 
first three can easily be referred to concrete standards available 
for reference at any part of the earth, but this reference is more 
difficult in the case of the fourth. The motion of the earth gives 
the mean solar second, a standard foot can be carried to any part 
of the earth, and if immersed in a mixture of ice and water, will 
have everywhere the same length ; and a standard pound has the 
same mass to whatever place it is carried. But no material 
standard of force is easily provided, so that it is philosophical to 
make this the dependent unit, and define it in terms of the others ; 
and this plan is that which has recently been followed. 
Convenience of expression, however, requires several units of 
each kind. It is not convenient to express the distance from 
Liverpool to New York in inches, nor the diameter of a rifle 
bullet in decimals of a mile. Names have accordingly been pro- 
vided for several units of time, length, and mass ; but a similar 
provision has not yet been made in the case of units of force. 
With the exception of two letters by the author of the present 
paper that appeared in NATURE March 2 and May 4 of the pre- 
sent year, and another letter by Mr. Thomas Muir, no names for 
units of force dependent on specified units of time, length, and 
mass, seem ever to have been publicly proposed. 
The unit of work stands in a simple relation to the units of 
force and length. It is the work done by unit force working 
through unit length. And that amount of energy which, in 
undergoing complete transformation, performs unit work, is the 
unit of energy. The same unit which measures work therefore 
measures energy. The only approach to a name that has been 
suggested on this subject is the ‘‘ British absolute unit of energy,” 
and the defect of nomenclature becomes often intolerable. 
The author therefore repeated the proposals which had already 
appeared in NATURE, so that we need only briefly recapitulate a 
portion of the names proposed. The unit of force, correspond- 
ing to a second, a metre, and a gramme, as units of time, length, 
and mass, was called a dyve; the kilodyne was a thousand dynes, 
the megadyne a million dynes. The unit of energy or work was 
called the Jove, and depended on the dyne and metre, the kilo- 
pone was a thousand pones, &c. In connection with the British 
system, the ‘British absolute unit force”? was called a hint, 
dependent on the pound, foot, and second, and the name erg 
was given to the corresponding unit of energy, the thousand and 
million ergs being written kilerg and pollerg respectively. 
The dyne is about the terrestrial gravitating force of 1} grains, 
the kilodyne of + lb., the megadyne of 2 cwt., and the kinit of 
4 0z. The kilopone is about ;'; of a kilogrammetre, the mega- 
pone about 723 foot-pounds, the kilerg is 31 foot-pounds, and the 
pollerg about the work done bya horse in a minute. On this 
subject a joint committee was appointed with Section G to frame 
a nomenclature of absolute units of force and energy. 
On the general Circulation and Distribution of the Atmosphere, 
by Prof. J. D. Everett, D.C.L. 
The object of this paper was to call the attention of meteoro- 
logists to a theory which is jointly due to Prof. J. Thomson of 
Belfast and Mr. Ferrel of Boston, U.S.A., and which gives the 
only satisfactory account of the grand currents of the atmosphere, 
and of the distribution of barometric pressure over the earth’s 
surface, the irregularities arising from the distribution of land 
and water being neglected. Independent proofs were also given 
of some of Mr. Ferrel’s results. 
A body moving along the earth’s surface with relative velocity 
v (units a foot and second) tends to describe a curve concave to 
the right of the body in the northern and to its left in the 
southern hemisphere, the radius of curvature being — feet. 

sin 
The deflection from a parallel of latitude into a great circle is 
usually negligible in comparison, being represented by the curva- 
ture of a circle of radius & cot A, 2 being the earth’s radius. 
To keep therefore the moving body in a great circle or in a 
parallel of latitude requires a constraining accelerating force 
cones and this formula applies alike to all horizontal 
directions of motion. 
The air over the extra-tropical parts of the earth has a relative 
motion towards the east, and therefore passes towards the 
equal to 
